A wearable electronic device may include a set of sensors for determining a set of biological parameters of a user that wears the wearable electronic device. Circuitry associated with the set of sensors may generate, for example, electrical signals or measurements corresponding to voltages at, forces applied to, or amounts of light incident on, the sensors. The various signals or measurements may be correlated to, or used to derive, various biological parameters of the user, such as a heart rate of the user.